Printed circuit board and manufacturing method thereof

ABSTRACT

A printed circuit board including: an insulation layer; a first circuit pattern formed over one surface of the insulation layer, the first circuit pattern having a side thereof slanted with respect to the insulation layer; and a second circuit pattern formed over the other surface of the insulation layer, the second circuit pattern having a side thereof slanted with respect to the insulation layer, wherein the side of the second circuit pattern is less slanted than the side of the first circuit pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. divisional application filed under 37 CFR1.53(b) claiming priority benefit of U.S. Ser. No. 12/213,703 filed inthe United States on Jun. 23, 2008, which claims earlier prioritybenefit to Korean Patent Application No. 10-2008-0000799 filed with theKorean Intellectual Property Office on Jan. 3, 2008 the disclosures ofwhich are incorporated herein by reference.

BACKGROUND

1. Field

The present invention relates to a printed circuit board and to a methodof manufacturing the printed circuit board.

2. Description of the Related Art

Electronic equipment are being produced with higher performance andsmaller sizes, leading to cost increases in such electronic equipment.As such, there are efforts to lower the cost of components used inelectronic equipment.

Methods of manufacturing a printed circuit board according to therelated art include tenting processes and additive processes.

Whereas tenting processes allow low manufacture costs, they are limitedin forming fine-line circuit patterns. Additive processes have beendeveloped to overcome this limitation, but these have the disadvantageof incurring higher costs.

In the related art, when a copper clad laminate (CCL) is used as thematerial for manufacturing a printed circuit board, the method used mayinvolve applying a tenting process on both surfaces or applying anadditive process on both surfaces. One reason for this may be that bothsurfaces would be exposed to the etchant or the plating bathsimultaneously. Thus, even in cases where a fine-line circuit pattern isrequired on one surface only, the same process may have to be employedfor both surfaces at the same time.

In the manufacture of a printed circuit board according to the relatedart, there may also be problems of curling or bending, etc., as thethickness of the printed circuit board is decreased.

SUMMARY

An aspect of the invention provides a method of forming circuit patternssequentially on both surfaces of a printed circuit board.

Another aspect of the invention provides a method of manufacturing aprinted circuit board that includes forming a first protective layerover one surface of a core substrate, forming a first circuit patternover the other surface of the core substrate by a first process,removing the first protective layer, forming a second protective layerover the other surface of the core substrate, and forming a secondcircuit pattern over the one surface of the core substrate by a secondprocess.

Still another aspect of the invention provides a method of manufacturinga printed circuit board that includes attaching one surface of each of apair of core substrates onto either surface of a first protective layer,forming a first circuit pattern over the other surface of each of thepair of core substrates by a first process, separating the pair of coresubstrates from the first protective layer, attaching the other surfaceof each of the pair of core substrates onto either surface of a secondprotective layer, and forming a second circuit pattern over the onesurface of each of the pair of core substrates by a second process.

Certain embodiments of the invention may include one or more of thefollowing features.

In certain embodiments, the core substrate can be a copper clad laminate(CCL).

The first process can be any one selected from a group consisting of atenting process, a semi-additive process, and an additive process.

The second process can be any one selected from a group consisting of atenting process, a semi-additive process, and an additive process.

The first and second protective layers can be foam tapes.

A side of the second circuit pattern may be less slanted than a side ofthe first circuit pattern.

An interface can be formed within the first circuit pattern.

Yet another aspect of the invention provides a printed circuit board,which includes an insulation layer, a first circuit pattern having aside slanted with respect to the insulation layer that is formed overone surface of the insulation layer, and a second circuit pattern havinga side slanted with respect to the insulation layer that is formed overthe other surface of the insulation layer. The side of the secondcircuit pattern may be less slanted than the side of the first circuitpattern.

In certain embodiments of the printed circuit board, an interface can beformed within the first circuit pattern.

Additional aspects and advantages of the present invention will be setforth in part in the description which follows, and in part will beobvious from the description, or may be learned by practice of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating the manufacture of a printed circuitboard according to an embodiment of the invention.

FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are cross sectionalviews representing a flow diagram illustrating the manufacture of aprinted circuit board according to an embodiment of the invention.

FIG. 8 is a flowchart illustrating the manufacture of a printed circuitboard according to another embodiment of the invention.

FIG. 9, FIG. 10, FIG. 11, FIG. 12, FIG. 13, and FIG. 14 are crosssectional views representing a flow diagram illustrating the manufactureof a printed circuit board according to another embodiment of theinvention.

FIG. 15 is a cross sectional view of a printed circuit board accordingto yet another embodiment of the invention.

DESCRIPTION OF EMBODIMENTS

The printed circuit board and method of manufacturing the printedcircuit board according to certain embodiments of the invention will bedescribed below in more detail with reference to the accompanyingdrawings. Those components that are the same or are in correspondenceare rendered the same reference numeral regardless of the figure number,and redundant explanations are omitted.

FIG. 1 is a flowchart illustrating the manufacture of a printed circuitboard according to an embodiment of the invention, and FIG. 2 throughFIG. 7 are cross sectional views representing a flow diagramillustrating the manufacture of a printed circuit board according to anembodiment of the invention. In FIGS. 2 to 7, there are illustrated acore substrate 11, an insulation layer 111, copper foils 112, a firstprotective layer 12, via holes 13, a first circuit pattern 14, vias 15,a second protective layer 16, and a second circuit pattern 17.

Operation S11 may include forming a first protective layer 12 over onesurface of a core substrate 11, where FIG. 2 represents a correspondingprocedure.

The core substrate 11 can be made from just the insulation layer. Thisparticular embodiment, however, illustrates the use of a copper cladlaminate (CCL). The copper clad laminate (CCL) can include a copper foilon just one surface of the insulation layer, or as illustrated in thisparticular embodiment, include copper foils 112 stacked over bothsurfaces of the insulation layer 111.

The thickness of a copper foil 112 can be such that allows theapplication of a tenting process. Also, the copper foil can be such thatis thin enough to allow the application of a semi-additive process.

A tape, such as a foam tape, can be used for the first protective layer12, whereby the surface of the core substrate 11 can be protected in asimple manner from a plating liquid or etchant, etc., making it possibleto form each of the first circuit pattern 14 and second circuit pattern17 in order.

Operation S12 may include forming a first circuit pattern 14 over theother surface of the core substrate 11 using a first process, where FIG.3 and FIG. 4 represent corresponding procedures.

Before forming the first circuit pattern 14, via holes 13 can beperforated, as illustrated in FIG. 3, in order to form vias 15 thatconnect the circuit patterns 14, 17 on either surface. A laser can beused for perforating the via holes 13. Afterwards, the insides of thevia holes 13 can be plated to form the vias 15.

The first process can be any of a semi-additive process, tentingprocess, and additive process. In this particular embodiment, the firstcircuit pattern 14 may be formed by a tenting process. In cases wherethe core substrate 11 is made only of an insulation layer, an additiveprocess may be used. An additive process may include selectively forminga circuit pattern over the insulation layer by electroless plating orelectroplating. A semi-additive process may include selectively forminga circuit pattern over a thin film of copper, and then removing theexposed copper by etching.

Operation S13 may include removing the first protective layer 12. Thefirst protective layer 12 can be physically separated or can be removedusing a chemical solution. If a foam tape is used for the firstprotective layer 12, increasing the temperature can create bubbles inthe tape, so that the adhesion may be lowered and the tape may easily beseparated from the core substrate 11.

Operation S14 may include forming a second protective layer 16 over theother surface of the core substrate 11, where FIG. 5 represents acorresponding procedure.

The other surface of the core substrate 11 may already have the firstcircuit pattern 14 formed by the first process. Therefore, the secondprotective layer 16 can be attached to the other surface of the coresubstrate 11, in order that the first circuit pattern 14 may not bedamaged. The second protective layer 16 can be made from the samematerial as that of the first protective layer 12.

Operation S15 may include forming a second circuit pattern 17 over theone surface of the core substrate 11 using a second process, where FIG.6 represents a corresponding procedure.

The one surface of the core substrate 11 may be exposed, after theremoval of the first protective layer 12. In this particular embodiment,the core substrate 11 may be a copper clad laminate, and thus a copperfoil 112 may be exposed as illustrated in FIG. 5.

The second process can be a tenting process of removing portions of thecopper foil 112. If the copper foil is thin, it is possible to form thesecond circuit pattern 17 by a semi-additive process and then remove theexposed portions of the copper foil. If the one surface of the coresubstrate 11 is the insulation layer, an additive process can be usedfor forming the second circuit pattern 17.

In this particular embodiment, the first circuit pattern 14 can beformed using an additive or a semi-additive process, and the secondcircuit pattern 17 can be formed using a tenting process, so that thesides of the second circuit pattern 17 can form lower inclinations, withrespect to the insulation layer 111, than the sides of the first circuitpattern 14.

One reason for this may be that, because of the tenting process, theupper portions on the sides of the second circuit pattern 17 may beexposed more to the etchant than are the lower portions and may thus beremoved more.

The first circuit pattern 14, on the other hand, can have an interfaceformed within, because of the additional plating procedure included forforming the vias 15.

Afterwards, the second protective layer 16 can be removed, and solderresists can be applied, to complete the printed circuit board 10 asillustrated in FIG. 7.

FIG. 8 is a flowchart illustrating the manufacture of a printed circuitboard according to another embodiment of the invention, and FIG. 9through FIG. 14 are cross sectional views representing a flow diagramillustrating the manufacture of a printed circuit board according toanother embodiment of the invention. In FIGS. 9 to 14, there areillustrated core substrates 21, insulation layers 211, copper foils 212,a first protective layer 22, via holes 23, first circuit patterns 24,vias 25, a second protective layer 26, and second circuit patterns 27.

Operation S21 may include attaching one surface of each of a pair ofcore substrates 21 to either surface of a first protective layer 22.FIG. 9 represents a corresponding procedure.

In this particular embodiment, the pair of core substrates 21 can beattached to both surfaces of the first protective layer 22 in asymmetrical arrangement.

The core substrates 21 can be made from just the insulation layers. Thisparticular embodiment illustrates the use of copper clad laminates(CCL). A copper clad laminate (CCL) can include a copper foil on justone surface of the insulation layer, or as illustrated in thisparticular embodiment, include copper foils 212 stacked over bothsurfaces of the insulation layer 211.

The thickness of a copper foil 212 can be such that allows theapplication of a tenting process. Also, the copper foil can be such thatis thin enough to allow the application of a semi-additive process.

A tape, such as a foam tape, can be used for the first protective layer22, whereby the surfaces of the core substrates 21 can be protected in asimple manner from a plating liquid or etchant, etc., making it possibleto form each of the first circuit patterns 24 and second circuitpatterns 27 sequentially.

Operation S22 may include forming a first circuit pattern 24 over theother surface of each of the pair of core substrates 21, where FIG. 10and FIG. 11 represent corresponding procedures.

Before forming the second circuit patterns 27, via holes 23 can beperforated, as illustrated in FIG. 10, to form vias 25 for connectingthe circuit patterns 24, 27. A laser can be used for perforating the viaholes 23. Afterwards, the insides of the via holes 23 can be plated toform the vias 25.

The first process can be any of a semi-additive process, tentingprocess, and additive process. In this particular embodiment, the firstcircuit patterns 24 may be formed by a tenting process. In cases wherethe core substrates 21 are made only of insulation layers, an additiveprocess may be used. An additive process may include selectively forminga circuit pattern over the insulation layer by electroless plating orelectroplating. A semi-additive process may include selectively forminga circuit pattern over a thin film of copper, and then removing theexposed copper by etching.

Operation S23 may include separating the pair of core substrates 21 fromthe first protective layer 22. The first protective layer 22 can bephysically separated or can be removed using a chemical solution. If afoam tape is used for the first protective layer 22, increasing thetemperature can create bubbles in the tape, so that the adhesion may belowered and the tape may easily be separated from the core substrates21.

Operation S24 may include attaching the other surface of each of thepair of core substrates 21 to either surface of a second protectivelayer 26, where FIG. 12 represents a corresponding procedure.

The other surface of each core substrate 21 may already have the firstcircuit pattern 24 formed by the first process. Therefore, the secondprotective layer 26 can be attached to the other surface of each coresubstrate 21, in order that the first circuit pattern 24 may not bedamaged. The second protective layer 26 can be made from the samematerial as that of the first protective layer 22. In this embodiment,the pair of core substrates 21 can be attached to the second protectivelayer 26 symmetrically.

Operation S25 may include forming a second circuit pattern 27 over theone surface of each of the pair of core substrates 21 using a secondprocess, where FIG. 13 represents a corresponding procedure.

One surface of each of the pair of core substrates 21 may be exposed,after the removal of the first protective layer 22. In this particularembodiment, the core substrates 21 may be copper clad laminates, andthus the copper foils 212 may be exposed, as illustrated in FIG. 12.

The second process can be a tenting process of removing portions of thecopper foils 212. If the copper foils are thin, it is possible to formthe second circuit patterns 17 by a semi-additive process and thenremove the exposed portions of the copper foils. If the one surface ofeach of the core substrates 21 is an insulation layer, an additiveprocess can be used for forming the second circuit patterns 27.

Since the first circuit patterns 24 can be formed using an additive or asemi-additive process, and the second circuit patterns 27 can be formedusing a tenting process, the sides of the second circuit patterns 27 canform lower inclinations with respect to the insulation layer 211,compared to the sides of the second circuit patterns 27.

One reason for this may be that, because of the tenting process, theupper portions on the sides of the second circuit patterns 27 may beexposed more to the etchant than are the lower portions and may thus beremoved more.

The first circuit patterns 24, on the other hand, can each have aninterface formed within, because of the additional plating procedureincluded for forming the vias 25.

Afterwards, the second protective layer 26 can be removed, and solderresists can be applied, to complete a pair of printed circuit boards 20as illustrated in FIG. 14. Each printed circuit board 20 can be acomplete product in itself.

FIG. 15 is a cross sectional view of a printed circuit board accordingto yet another embodiment of the invention. In FIG. 15, there areillustrated a printed circuit board 30, an insulation layer 31, a firstcircuit pattern 33, a second circuit pattern 32, and vias 34.

The printed circuit board 30 according to this embodiment may have afirst circuit pattern 33 and a second circuit pattern 32 formedrespectively on either surface. The second circuit pattern 32 can beformed by a tenting process, so that the sides 321 of the second circuitpattern 32 can be slanted with respect to the insulation layer 31.

The sides 331 of the first circuit pattern 33, however, may be slantedby a greater inclination from the insulation layer 31 compared to thesides 321 of the second circuit pattern 32, as the first circuit pattern33 can be formed by an additive or a semi-additive process.

A tenting process can involve removing unnecessary portions with anetchant and having the remaining portions form the circuit pattern.Here, the upper portions of the circuit pattern can be exposed more tothe etchant and thus can be removed more. Therefore, the sides 321 ofthe second circuit pattern 32 can form a smaller inclination with theinsulation layer 31 compared to those of the first circuit pattern 33,as is illustrated in FIG. 15.

The first circuit pattern 33 can have an interface 36 formed within,because of the extra plating procedure involved in forming the vias 34.

According to certain aspects of the invention as set forth above,circuit patterns can be formed sequentially on either surface of aprinted circuit board, making it possible to apply a different processfor forming the circuit pattern on each surface of the printed circuitboard.

While the spirit of the invention has been described in detail withreference to particular embodiments, the embodiments are forillustrative purposes only and do not limit the invention. It is to beappreciated that those skilled in the art can change or modify theembodiments without departing from the scope and spirit of theinvention. As such, many embodiments other than those set forth abovecan be found in the appended claims.

1. A printed circuit board comprising: an insulation layer; a firstcircuit pattern formed over one surface of the insulation layer, thefirst circuit pattern having a side thereof slanted with respect to theinsulation layer; and a second circuit pattern formed over the othersurface of the insulation layer, the second circuit pattern having aside thereof slanted with respect to the insulation layer, wherein theside of the second circuit pattern is less slanted than the side of thefirst circuit pattern.
 2. The printed circuit board of claim 1, whereinan interface is formed within the first circuit pattern.